1. Field of the Invention
The present invention relates to photoresist monomers, polymers derived therefrom, and photoresist compositions comprising the polymers. In particular, the present invention relates to dipropargyl malonic acid cyclic isopropylidene ester photoresist monomer, polymers and compositions suitable for photolithography processes employing KrF, ArF, EUV, and preferably 157 nm light sources like VUV.
2. Description of the Background Art
Recently, chemical amplification-type deep ultraviolet (DUV) photoresists have been investigated in order to achieve high sensitivity in minute image formation processes for preparing semiconductor devices. Such photoresists are prepared by blending a photoacid generator and a matrix resin polymer having an acid labile group.
In a photolithography process, exposure of a photoresist to light of a particular wavelength generates an acid from the photoacid generator that is present in the photoresist. This acid causes the main chain or the branched chain of the resin to decompose or become cross-linked. In addition, the acid removes the acid labile group and changes the polarity of the photoresist in the exposed region. This polarity change creates a solubility difference between the exposed portion and the unexposed portion in a developing solution, thereby allowing a pattern formation. The resolution of the pattern that is formed depends on the wavelength of the light source, i.e., in general a shorter wavelength allows formation of more minute patterns.
In general, a useful photoresist (hereinafter, abbreviated as xe2x80x9cPRxe2x80x9d) has a variety of desired characteristics, such as an excellent etching resistance, heat resistance and adhesiveness. In addition, a photoresist should be easily developable in a commercially readily available developing solution, such as 2.38% aqueous tetramethylammonium hydroxide (TMAH) solution. Furthermore, it should provide a good pattern formation using a 157 nm wavelength light source. However, it is difficult to synthesize a photoresist polymer that satisfies all of these desired characteristics. For example, polymers having a polyacrylate polymer backbone are readily available, but they have a poor etching resistance, difficult to develop, and difficult to obtain a good minute pattern due to its poor transmittance at wavelength of 157 nm.
It is an object of the present invention to provide photoresist monomers having an excellent transmittance at 157 nm wavelength, etching resistance, adhesiveness and photosensitivity.
Another object of the present invention is to provide PR polymers derived from such photoresist monomers and methods for preparing the same.
Yet another object of the present invention is to provide photoresist compositions comprising such PR polymers.
Still another object of the present invention is to provide a semiconductor device produced by using the above described PR composition.